Reverse T3 is a hot topic on YT. There are plenty of docs talking about how they use it. They imply - or state emphatically - that docs not using it is "behind the times", "not keeping up". Reverse T3 is real. It's a variation of thyroid hormone. And it truly is an inactivated version of the thyroid hormone. In addition, it is also increases during several conditions.

Two of those conditions are often mentioned by the "new age" Youtube docs:

1. malnutrition, or decreased caloric intake. In fact, this does appear to be a key mechanism for slowing Basal Metabolic Rate; and

2. During significant illness, as in hospital ICU-related illness. Direct T3 might be only slightly depressed, or not low at all. However, the Reverse T3 is clearly elevated, and the patient is clearly hypothyroid by the clinical condition - or symptoms.

Reverse T3 is also elevated in 2 other states: 1. during fetal development (high T3 is destructive of fetal development); and 2. with large hemangiomas - ( the D3 de-iodinase enzyme is found in high concentrations in hemangioma tissue.

The following link is a great source for learning the basics and history of Reverse T2 as well as thyroid science.

https://www.ccjm.org/#

Does all this mean that Reverse T3 is real and that high values are key to a diagnosis for your fatigue? Not so fast - the theory is good. But these things have been knowing for years - if not decades. At this point, however, the scientific evidence gets thin. The jury really is still out on this issue. I have used reverse T3, mostly at the request of patients. But I'd not recommend using reverse T3 levels to prescribe medications.

And the fortunate part is this - most docs, no matter how vocal they are about reverse T3, use it to recommend lifestyle changes - not medications.